Spent Fuel Management

The terms used nuclear fuel and spent nuclear fuel are both used to describe nuclear fuel that has been used in a nuclear reactor. There is no liquid in used nuclear fuel. Used nuclear fuel is a solid material, in the form of ceramic pellets. Each pellet is about the size of a pencil eraser. The pellets are stacked inside long metal zirconium tubes approximately 12 feet long, which are sealed on each end to form a fuel rod. Between 100 and 300 fuel rods are arranged in a square pattern to form a fuel assembly. Depending on the design, a reactor core may have between 120 and 800 fuel assemblies. A used fuel storage cask may contain up to 89 fuel assemblies. Learn more about nuclear fuel by watching this Nuclear Energy Institute video.

A single nuclear fuel assembly spends around five years in the reactor of a nuclear plant, creating heat that is then turned into electricity. Typically, every 18 to 24 months, a nuclear plant stops generating electricity to replace a third of the fuel assemblies in the reactor with fresh ones. The assemblies removed from the reactor are then stored in a large body of water inside the nuclear plant, called the spent fuel pool, where they cool over time. The water also shields the workers from the radiation that comes from the fuel assemblies. Due to the use of water, this storage method is also often referred to as “wet storage”.

After the used fuel assemblies have cooled for at least one year, they may be moved from the pool to canisters made from stainless steel filled with an ‘inert gas,’ i.e. a gas that does not chemically react and prevents corrosion of the content of the canister, such as Helium. The steel canisters are strength welded closed in order to provide a leak-tight containment of the used nuclear fuel and are placed inside large robust casks made of steel and concrete.

The steel and concrete casks surrounding the canister provide radiation shielding to workers and the public from the stored used nuclear fuel, and physical protection of the fuel. The casks are then initially stored at the site of the nuclear plant. Since this storage method does not require any water, it is often referred to as “dry storage”. It also does not use any fans for cooling and electric power is not required.

The incidence of damage to nuclear fuel assemblies during their time in the reactor core has been trending down steadily over the years as improved materials, designs and operational conditions have been developed and used. Nevertheless, a small fraction of commercial nuclear fuel assemblies may still be damaged during its burn in the reactor. However, Holtec’s dry storage and transport systems have the ability to safely store and transport used nuclear fuel that is considered damaged. In fact, Holtec’s dry storage systems are already safely storing damaged used fuel in various locations right now.

Even though the plant owner knows the state of its fuel in wet storage, prior to placing a used fuel assembly into dry storage, each fuel assembly is inspected for damage. If an assembly is damaged, additional special packaging is used for that assembly within the dry storage system.

The plant knows the state of its fuel in wet storage and only a small fraction of commercial nuclear fuel has been damaged during its burn in the reactor. If an assembly is thought to be too fragile to maintain its configuration during handling, it can still be loaded into dry storage systems, using special tooling designed and manufactured by Holtec to safely lift the used nuclear fuel assembly into the dry storage system. For any assembly that is damaged, additional special packaging is used within the dry storage system.

If an assembly is damaged or suspected of being damaged, additional special packaging is used for that assembly within the dry storage system.

A fuel assembly is thoroughly inspected prior to placement into a dry storage canister. After placement of assemblies into the canister, the canister is fully strength welded closed, dried and then filled with inert gas such as helium. The presence of inert gas does not allow any deterioration of the stored spent fuel.

Independent Spent Fuel Storage Installations, or ISFSIs, are facilities that are designed and constructed for the interim storage of spent nuclear fuel. These facilities are licensed separately from nuclear power plants and are considered independent even though they may be located on the site of a nuclear power plant or another NRC-licensed facility. They are designated and qualified for interim use only, i.e. for spent fuel storage until a final repository for spent fuel is available.

MRS is an acronym for a monitored retrievable storage facility. It means an interim storage site where the condition of the fuel package is subject to monitoring. The Nuclear Waste Policy Act mentions (one or more) MRS as an alternative to a repository.

The AFR means an away from reactor storage. There is effectively no AFR in America, with all storage sites on the reactors’ premises.

Holtec has already licensed transportation casks for shipping canisters from ISFSIs and they can be made available as soon as the U.S. Department of Energy is ready to ship fuel to a repository.

The U.S. Government, through the U.S. Department of Energy, has, by law, the ultimate responsible for the transportation and final disposition of spent nuclear fuel. In support of this, Holtec International and its partner, the Eddy-Lea Energy Alliance (ELEA), LLC, have launched the licensing of an autonomous consolidated interim storage facility (CISF) in southeastern New Mexico on land owned by ELEA, LLC. The facility, named HI-STORE CISF, will provide a significant step on the path to the Federal Government’s long standing obligation for disposition of used nuclear fuel by providing a safe, secure, temporary, retrievable, and centralized facility for storage of used nuclear fuel and high-level radioactive waste until such time that a permanent solution is available. The principal goal of the HI-STORE CISF is to provide a site to aggregate the used nuclear fuel canisters presently stored across the country into one secure location.

CIS is an acronym of consolidated interim storage. A CIS is also a monitored facility, i.e., a MRS. The DOE used the term CIS in its policy announcement on interim storage of used nuclear fuel.

Holtec International and its partner, the Eddy-Lea Energy Alliance (ELEA), LLC, have launched the licensing of an autonomous consolidated interim storage facility (CISF) in southeastern New Mexico on land owned by ELEA, LLC. The facility, named HI-STORE CISF, will provide a significant step on the path to the Federal Government’s long standing obligation for disposition of used nuclear fuel by providing a safe, secure, temporary, retrievable, and centralized facility for storage of used nuclear fuel and high-level radioactive waste until such time that a permanent solution is available. The HI-STORE CISF provides a site to aggregate the used nuclear fuel canisters presently stored across the country at independent used fuel storage installations into one secure location.

The license application for the HI-STORE CISF was submitted to the USNRC on March 31, 2017 and accepted by the USNRC in February 2018 (USNRC Docket No. 72-1051). It is anticipated that the HI-STORE CISF license will be issued by the NRC in mid-2021. The HI-STORE CISF will utilize Holtec’s licensed HI-STORM UMAX, an underground dry storage system engineered and sized to hold all currently licensed dry spent fuel storage canisters throughout the U.S.

The initial application for the HI-STORE facility includes storage of up to 8,680 metric tons of uranium in commercial used fuel (500 canisters) with future amendments for additional canisters up to 10,000 storage locations. The U.S. currently has more than 80,000 metric tons of used nuclear fuel in storage and more is being generated every day at a rate of 2,000 metric-tons per year.

Yes, Holtec is the largest spent fuel vendor in the country. Of the 120 commercial nuclear plants (operating and shutdown), 59% rely on Holtec’s technology for spent fuel storage and transportation. From an operating plant perspective, 64% of the 95 operating commercial nuclear plants use Holtec’s technology for spent fuel storage and transportation.

Worldwide, over 130 nuclear plants rely on Holtec’s technology for spent fuel storage and transportation. In addition, over 35 nuclear plants worldwide currently rely on Holtec to perform the loading services of the Holtec supplied spent fuel storage systems.

Protection of the environment and safety of the local community during decommissioning are Holtec’s foremost objectives. Our procedures and practices are geared to ensure public health and safety as we safely and efficiently decommission nuclear plants.

Holtec does several things to serve the local communities that differentiate us as a leading decommissioning contractor. From a local perspective, Holtec begins the decommissioning process much sooner helping to maintain jobs and creating additional jobs through the local union halls. From a technology perspective, Holtec has developed new innovative package designs for waste of all different classes (i.e. different levels of radioactivity) that have three to five times the volume capacity being used in the industry today. These super-capacity containers will drastically reduce the number of required shipments (by road, rail or water) to complete any site’s cleanup. Fewer shipments mean less traffic and less burden on the local infrastructure. Another respect in which our decommissioning program is uniquely environment-friendly is our approach to minimize the amount of waste by diligent, surgical separation of the waste categories. Holtec removes the radioactive layer to the extent practicable returning the uncontaminated material to commercial use. This environmentally conscious program of waste segregation will prevent millions of pounds of uncontaminated material from being commingled with contaminated materials.

Since the reactor is no longer running, the risk of an event occurring decreases significantly. This risk decreases even further when the spent fuel is moved into dry storage. Once this occurs, the decommissioning project technically becomes an industrial demolition project.

Yes, Holtec utilizes nuclear science expertise for reactor segmentation. Nuclear scientists calculate the neutron bombardment on the different elevations of the reactor during its operating life very precisely. For this purpose, experimentally validated computer codes are used. This enables Holtec to segregate the reactor vessel parts by their radioactivity content helping to minimize the quantity of highly activated waste. This effort is another example of our responsible stewardship of the environment.

Holtec has a number of patented transport package designs that the company will use to ship contaminated materials to facilities licensed to receive the respective materials. The package type used for transporting the waste depends on its radioactivity level which is often stated in curies. The package design must meet the NRC and Department of Transportation (DOT) requirements, which essentially guarantee that the dose received by a person in the vicinity of the transport vehicle will be less than the cosmic and terrestrial radiation that bathes the land all hours of the day and night.

The operating procedures, based on Holtec’s Fleet Management Model, emphasize control of contamination as a cardinal guiding principle. An important activity in this area is our effort to remove fuel from the pool and place it into dry storage at the earliest possible date. Holtec has developed an array of high-heat dissipation canisters that comply with the NRC’s regulations, which will enable us to safely move fuel out of the pool on a schedule considered to be impossible only a few years ago. By safely emptying the pool of fuel sooner, the spent fuel pool water can be permanently removed as a potential source of site contamination.

Decommissioning activities are not expected to impact the pipelines or transmission lines near the site. Should remediation require clean-up in the areas adjacent to these utilities, we will coordinate with the utility to ensure the work is performed in a safe and compliant manner. Decommissioning activities will be carried out under controlled work processes and procedures that will ensure no vital systems, structures or components at the site (such as gas lines and power transmission lines) are damaged or their functionality compromised.

It is highly unlikely a terrorist group could steal used fuel and create a dirty bomb. Robust security measures are required by law at facilities regulated by the U.S. NRC. The specific security capabilities required by the NRC are compartmented, and not available to the general public. It can be said that the measures include a well-trained and armed security force, physical barriers, proper lighting, and intrusion detection and surveillance systems.

Keeping the used fuel at the site means the entire site could not be released for future use. Though other parcels could be released, the Independent Spent Fuel Storage Installation would remain.  To facilitate moving used fuel offsite, Holtec is in the process of licensing a consolidated interim storage facility called HI-STORE in Southeastern New Mexico,  which can enable every site in the country to ship its used fuel offsite. Holtec expects the NRC to make its licensing decision in 2021. Pending an agreement(s) with the U.S. Department of Energy, nuclear utilities or another funding source, construction could start in 2021/2022 and be complete in 2024. The HI-STORE CIS could be ready to accept its first shipment in 2024.

Dry cask storage is safe for people and the environment. Cask systems are designed to contain radiation, manage heat and prevent nuclear fission. They resist earthquakes, projectiles, tornadoes, floods, temperature extremes and other natural and manmade scenarios. The heat generated by a loaded spent fuel cask is typically less than that given off by a home-heating system. The heat and radiation naturally decrease over time without the need for fans or pumps. The casks are under constant monitoring and surveillance.

The statement that canisters are only designed for 20 to 40 years is not correct. Canisters were initially licensed by the Nuclear Regulatory Commission for 20 years, since that was considered sufficient at that time; however, the canisters are designed to last for hundreds of years. Several years ago, this maximum licensing period was in fact changed from 20 to 40 years by the NRC. For the first 20 years of use, no monitoring or inspection programs are needed. After the initial licensing period, the vendor can apply for a license renewal for an additional 40 years which requires an adequate aging management program that includes inspections and maintenance.

The canisters that house the spent fuel only contain solid materials that do not generate any hydrogen and are thoroughly dried to avoid hydrogen generation from any remaining water. Further, they are filled with an inert, i.e. non-reactive, gas. A build-up of an explosive situation inside a canister is therefore not possible.

Yes, the warranty covers these items.

There are no exclusions to the warranty.

No, dry storage systems do not have pressure monitoring. The only circumstance in which the pressure inside a canister loaded with spent nuclear fuel would increase is if the cask’s ventilation paths would be blocked; there is no other credible scenario. To ensure that the ventilation paths remain open and clear, the paths are inspected on a regular schedule as mandated by the NRC.

Holtec canisters are designed to sustain significantly more internal pressure than it can ever experience from any of the expected or hypothetical off-normal and accident conditions considered in the safety analyses. Canisters are designed such that even under the assumed worst case accident condition, the rise in the total internal pressure will be only half or less of what the canister is designed to withstand.

The canister is fully welded, and therefore the system does not need or have any seals.

Since there is no credible situation for a pressure increase in a canister loaded with spent fuel, a pressure relief valve is not needed. Additionally, providing a relief valve “just in case” would create a possible vulnerability for leakage for the otherwise leak-tight canister. Therefore, because leak tightness of the canister is an overriding safety consideration, no relief valves are used, since they would provide no benefit and introduce unwanted vulnerabilities.

Several measures are taken during the fuel loading process to ensure there will be no need to re-open a welded canister. It is filled with an ‘inert gas’ (such as Helium), i.e. a gas that does not chemically react and that prevents any corrosion. Each canister is also leak-tested prior to use to ensure the inert environment will remain inside the canister. The inert environment prevents the stored spent fuel from degrading and eliminates the need to inspect the fuel or the interior of the canister.

Cracking of canisters or a crack that grows through the wall are not plausible scenarios. As part of the NRC’s license renewal, the inspection and aging management program requires surface inspections of canisters. If an issue were identified, there would be sufficient time to act, since corrosion is a very slow process. If any crack were to form, it would be detected as part of the inspection program before it could ever go through the wall of the canister. Chloride Induced Stress Corrosion Cracking (CISCC) has been identified as a potential mechanism of a long-term degradation, particularly in a marine environment, and the nuclear industry takes several precautions to prevent any degradation issues. Manufacturing techniques such as the reduced amount of welding needed on the canister and less heat from the welding process, and a robust inspection program are among the actions in place to mitigate CISC.

Holtec casks do not present any risk to the public and are as safe as any other cask system. Holtec casks are licensed by the U.S. Nuclear Regulatory Commission and designed and analyzed to meet the same stringent safety limits and criteria as all other casks by other suppliers in the United States. In addition to the United States where Holtec holds 13 certifications from the NRC, Holtec’s systems for storage and transport of used nuclear fuel have been vetted and independently accepted by nuclear regulators in 13 different countries.

Absolutely. Holtec’s dry storage and transport systems have been analyzed by agencies such as the Nuclear Regulatory Commission (NRC), Electric Power Research Institute, Sandia National Laboratory, as well as regulatory authorities in 13 different countries to validate the robustness of the systems to safely store and transport used nuclear fuel. Per NRC regulations, all security threats including terrorism are considered in the cask system safety analyses.
Holtec’s systems have been analyzed and demonstrated to withstand an aircraft crash. In accordance with the Swiss regulator’s storage certification requirement, a missile test was designed to simulate the impact of a crashing aircraft on the HI-STAR 180 transport cask while in use as a spent fuel storage device. The post-impact inspection of the cask showed that it weathered the impact with large performance margins. Watch the video of this test.

Cracking of canisters or a crack that grows through the wall are not plausible scenarios. In the unlikely event that a crack were to develop, technology is now available that will allow the canister to be repaired in place or repackaged by placing the impacted canister inside another canister. This is done without the need for a spent fuel pool or dry cell.

A cask system failure is not a plausible scenario. A cask system is a passive system meaning it has no active components or moving parts like a motor, pump or cooler that it relies on to function. The canister is filled with inert helium gas so that there is no mechanism for internal degradation of the canister or the used nuclear fuel. The canister is fabricated using high grade nuclear stainless steel; it is a well-known fact that there is no failure mechanism for stainless steel to suddenly fail without any symptoms. In addition, cask systems are required to be monitored by the U.S. Nuclear Regulatory Commission as part of the cask’s aging management program to ensure that degradation, if any is found over the years, is detected and corrected.

No, because the cracking of canisters or a crack that grows through the wall are not plausible scenarios. Since the canister is stored inside the cask overpack containing several layers of structural steel and several feet of concrete, there is no potential path for a leak in the canister to turn into a major radioactive release.

The failure modes of both canister and casks have been studied in detail by cask designers, the Nuclear Regulatory Commission and national laboratories and institutes such as the Electric Power Research Institute. These studies have shown that the degradation rate from corrosion is very slow and easily detectable. In addition, the technology is now available that will allow the canister to be repaired in place or repackaged by placing the impacted canister inside another canister.

Holtec’s dry storage systems are extremely robust, able to withstand all kinds of unusual and accident conditions that may be expected, up to and including disasters such as a crashing fighter plane. Under all conditions, the NRC requires dry storage systems to meet NRC safety requirements, including during and after an accident. Accident conditions include events from natural phenomena like earthquakes, burial under debris, lightning strikes, and other phenomena (e.g., seiches, tsunamis, and hurricanes). Principal requirements are that no radioactive material is released and that radiation dose rates remain within safety limits.

No. In the more than 40 years that dry storage systems have been in use, there has never been a release of radioactive material. There have been no known or suspected attempts to sabotage cask storage facilities. Tests on spent fuel and cask components after years in dry storage confirm that the systems are providing safe and secure storage. The NRC also analyzed the risks from loading and storing spent fuel in dry casks and found little to no potential health risks.

Holtec has developed and continues to develop new versions of the HI-STORM canister storage systems that are focused to meet specific user needs. For each site, the company recommends the most appropriate fuel storage system that accords with the architectural constraints of the nuclear plant and system performance requirements. Several plants are now using Holtec’s state of the art canisters with the basket that supports the fuel assemblies inside the canister made from Metamic, an aluminum boron carbide metal matrix composite material. This allows spent fuel that was in the spent fuel pool for less than three years to now being safely stored in the dry cask.

The storage casks are subject to visual surveillance or external temperature measurements on a pre-defined schedule to ensure that the cask’s flow vents are not obstructed. The design of the storage system is such that, absent an obstruction to the ventilation air flow, there is no physical mechanism for the temperature or pressure in the storage canister to rise uncontrollably. Additionally, the HI-STORM cask has been determined to maintain a large margin of safety with respect to the in-canister temperatures and pressures.

Yes, transportation of used nuclear fuel is safe because the shipping packages are very robust and because the shipments are highly regulated by the NRC and the Department of Transportation.

According to a U.S. Department of Energy (DOE) report prepared by the Oak Ridge National Laboratory and Argonne National Laboratory, more than 25,000 shipments of used nuclear fuel have been made worldwide to date, shipping more than 87,000 metric tons of fuel. Review of the data sources shows that all of these shipments were undertaken without any injury or loss of life.

In the U.S., except for a limited amount of transport, the majority of used nuclear fuel remains at the reactor sites. Nevertheless, more than 1,300 used fuel shipments have been completed safely over the past 35 years in the U.S., according to the NRC, with most shipments performed by rail. Thanks to the robust transportation cask designs and stringent safety measures adopted by the industry, every one of these used fuel shipments has been safely completed with no release of radioactivity or environmental damage.

Transportation casks for shipping used nuclear fuel are robustly designed to protect the public from releases of radioactive material in the unlikely event of an accident. The NRC regulates the design and construction of these casks by requiring that the candidate cask must demonstrate that it can survive four successive accident conditions involving free drop, puncture, fire and submersion in water events before it is considered fit for transportation. Casks, such as Holtec’s HI-STAR 190, HI-STAR 100 and HI-STAR 100MB are designed and fabricated with multiple layers of steel, lead and other materials to safely confine the fuel, shield workers and the public from radiation associated with the fuel. Inside the cask, the used nuclear fuel, in solid form, is confined inside a strength-welded canister, allowing no pathway for the radiological matter to escape to the environment. Hence multiple layers of protection stand between the cask’s contents and the environment. Fully loaded casks weigh 125 tons or more for rail shipments. Typically, for every ton of used fuel, a cask has about 4 tons of robust shielding material.

Absolutely. Holtec’s dry storage and transport systems have been analyzed by agencies such as the Nuclear Regulatory Commission (NRC), Electric Power Research Institute, Sandia National Laboratory, as well as regulatory authorities in 13 different countries to validate the robustness of the systems to safely store and transport used nuclear fuel. Per NRC regulations, all security threats including terrorism are considered in the cask system safety analyses.

Holtec’s systems have been analyzed and demonstrated to withstand an aircraft crash. In accordance with the Swiss regulator’s storage certification requirement, a missile test was designed to simulate the impact of a crashing aircraft on the HI-STAR 180 transport cask while in use as a spent fuel storage device. The post-impact inspection of the cask showed that it weathered the impact with large performance margins. Watch the video of this test.

Transportation of used nuclear fuel is strictly regulated by the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Transportation (DOT). Transportation containers are designed to protect the public from releases of radioactive material in the unlikely event of an accident. The NRC approves the design, fabrication, use and maintenance of shipping containers and regulates security of the spent fuel. The U.S. Department of Transportation regulates the shipping routes and transportation conveyances. Under current law, the U.S. Department of Energy (DOE) is responsible for shipping the used fuel from nuclear power plant sites to a specially designed repository for storage. According to the NRC, over the last 40 years, thousands of shipments of commercially generated spent nuclear fuel have been made throughout the U.S. without causing any radiological releases to the environment or harm to the public.

Each operating railroad is responsible for inspection and maintenance of track. This is audited by the Federal Railroad Administration (FRA) using established, procedure-based audit methods to assure compliance with regulations and performance requirements. Industry leads can be leased or owned by a specific customer who would then be responsible for inspection and maintenance of the leased portion of track.

Railroads are owned privately, and each individual railroad is responsible for maintenance and upkeep of their tracks. Industry tracks are sometimes in the ownership of the licensee or storage facility owner and maintenance is conducted through an agreement with the railroad. The federal government offers grants to build new track or repair track.

There is an upper limit of radiation dose emitting from the transport package that is limited by federal regulation. This creates an upper bounding radiation limit, such that no member of the public can be exposed to unacceptable levels of radiation no matter how close they are to the transport package, e.g., in the rail yard, at railway crossings etc. The limit is only slightly more than a typical chest x-ray and is not considered harmful. Actual dose rates vary depending on the cask, but are typically much lower than the upper limit. The NRC conducted a comprehensive risk analysis (NUREG – 2125, Spent Fuel Transportation Risk Assessment) for the transportation of spent nuclear fuel under routine and accident conditions. The analysis concluded the radiation dose to members of the public for routine spent fuels shipments would be less than 1/1000 the amount of radiation the general public receives from background radiation annually.

The American Association of Railroads (AAR) documents “Recommended Railroad Operating Practices for Transportation of Hazardous Materials” and “Railroad Hazmat Resource Tool Kit” outlining emergency response related to rail transport are provided below.

“AAR Circular OT-55-Q “Recommended Railroad Operating Practices for Transportation of Hazardous Materials”
“AAR BOE “Railroad Hazmat Resource Tool Kit”

Yes. Under NRC regulations, the shipper is required to conduct preplanning and provide advanced notification to any state that the shipment will enter or pass through.

Shipments of this type are carefully orchestrated and are route-controlled. The states are involved and pre-approve the transportation plans. States work with the shipper and rail carrier to determine the most practical and safe location to perform inspections.